In addition EXSLT.NET provides a proprietary set of useful extension functions. Find full list of supported extension functions and elements in the
"Extension Functions and Elements" section. For more info about EXSLT and EXSLT.NET see
References.

Additionally MvpXslTransform class has two properties -
SupportedFunctions and
MultiOutput, which allow you to control which features should be supported, for instance you can define that you need all extension function modules, but not multiple output support (the default settings) by setting SupportedFunctions and MultipleOutput
properies in your code before the call to the Transform() method:

3. Extension Functions and Elements

Full list of extension functions EXSLT.NET supports can be found
here.

Note: For compatibility, some extension functions (such as date:date-time()) have camelCased alias names, e.g. date:dateTime(). Both forms are equivalent names, referring to the same function implementation, although beware that alias names are non-standard
ones, so most likely they won't be recognized by other EXSLT implementations.

The only extension element supported is the
exsl:document element. See "Multiple Output" section for more info.

4. Multiple Output

EXSLT.NET partially supports
exsl:document extension element. Not all exsl:document attributes and their values are supported in this version of the EXSLT.NET. The supported subset of attributes and values is as follows:

exsl:document extension element is not supported when transformation is done to XmlReader or XmlWriter. In the latter case use overloaded Transform() method, which accepts instance of MultiXmlTextWriter class to transform to.

exsl:document extension element is supported through postprocessing of transformation result using customized XmlTextWriter class. This unconditionally assumes the transformation is always done in XML, so actually currently there is no way to produce real HTML
(not XHTML) result documents. More specifically, main result document is always XML, but subsidiary result documents may be written either as XML or as text, depending on the "method" attribute value of the appropriate exsl:document element.

Moreover, the xsl:output element is ignored. That only affects outputting of the main result document though, because the xsl:output element does not affect outputting of any subsidiary result documents. It's completely controlled by the exsl:document element.
Instead, you can get some control over outputting of the main result document using the MultiXmlTextWriter properties inherited from the XmlTextWriter class, particularly with encoding and indentation.